I4 REPTILES AND BIRDS. 
insects, small terrestrial or aquatic molluscs; others, such as 
Ophidians and Crocodiles, attack Birds, and even Mammals. Large 
Serpents, owing to the distensibility of their cesophagus, frequently 
swallow animals broader than themselves at the moment of seizing 
their prey. 
Reptiles, whether Batrachians, Ophidians, or Chelonians, are 
mostly ovzparous, sometimes ov0-viviparous, and generally very prolific. 
The eggs of some are covered with a calcareous envelope, as in the 
turtle. Sometimes they are soft, and analogous to the spawn of fish, 
as in the Batrachians. Most species do not hatch their eggs by sitting 
upon them, but bury them in the sand, trusting to the heat of the 
sun, which hatches them in due course. To this the Pythons form a 
partial exception. Batrachians content themselves with diffusing their 
spawn or eggs in marshy waters or ponds, or they bear them on their 
backs until the time of hatching approaches. On leaving the egg 
young Tortoises have to provide immediately for their own wants, for 
the parents are not present to bring them nourishment or to defend 
them against enemies. Parental affection, so manifest among the 
superior animals, does not exist in oviparous species, except in those 
that hatch their eggs in the body of the mother. The young are 
consequently, so to speak, produced in a living state, and fully pre- 
pared for the battle of life. The loves of these animals present none 
of that character of mutual affection and tender sympathy which dis- 
tinguishes the Mammalia and Birds.* When they have ensured the 
perpetuity of their species, they separate, and betake themselves again 
to their solitary existence. 
Some Reptiles attain dimensions truly extraordinary, which render 
them most formidable. Turtles are met with which weigh as much 
as 1,600 pounds; and carapaces have been found that measured as 
much as six feet in length. Although the average length of the 
Crocodile is about eight to nine feet, they have been seen twenty- 
four and even thirty feet long. 
In Chelonians the surface of the skull is continuous without 
movable articulations. The head is oval in the Land Tortoises, the 
interval between the eyes large and convex, the opening of the 
nostrils large, the orbits round. The general distinguishing character- 
istic of Tortoises is the external position of the bones of the thorax, 
at once enveloping with a cuirass or buckler the muscular portion of 
the frame, and protecting the pelvis and shoulder bones. ‘The ribs 
* Birds, however, are oviparous, and nevertheless manifest the strongest 
parental affection. —Ep. 
